1// Copyright 2009 The Go Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style
3// license that can be found in the LICENSE file.
4
5package aes
6
7import (
8	"crypto/cipher"
9	"crypto/internal/alias"
10	"crypto/internal/boring"
11	"strconv"
12)
13
14// The AES block size in bytes.
15const BlockSize = 16
16
17// A cipher is an instance of AES encryption using a particular key.
18type aesCipher struct {
19	l   uint8 // only this length of the enc and dec array is actually used
20	enc [28 + 32]uint32
21	dec [28 + 32]uint32
22}
23
24type KeySizeError int
25
26func (k KeySizeError) Error() string {
27	return "crypto/aes: invalid key size " + strconv.Itoa(int(k))
28}
29
30// NewCipher creates and returns a new [cipher.Block].
31// The key argument should be the AES key,
32// either 16, 24, or 32 bytes to select
33// AES-128, AES-192, or AES-256.
34func NewCipher(key []byte) (cipher.Block, error) {
35	k := len(key)
36	switch k {
37	default:
38		return nil, KeySizeError(k)
39	case 16, 24, 32:
40		break
41	}
42	if boring.Enabled {
43		return boring.NewAESCipher(key)
44	}
45	return newCipher(key)
46}
47
48// newCipherGeneric creates and returns a new cipher.Block
49// implemented in pure Go.
50func newCipherGeneric(key []byte) (cipher.Block, error) {
51	c := aesCipher{l: uint8(len(key) + 28)}
52	expandKeyGo(key, c.enc[:c.l], c.dec[:c.l])
53	return &c, nil
54}
55
56func (c *aesCipher) BlockSize() int { return BlockSize }
57
58func (c *aesCipher) Encrypt(dst, src []byte) {
59	if len(src) < BlockSize {
60		panic("crypto/aes: input not full block")
61	}
62	if len(dst) < BlockSize {
63		panic("crypto/aes: output not full block")
64	}
65	if alias.InexactOverlap(dst[:BlockSize], src[:BlockSize]) {
66		panic("crypto/aes: invalid buffer overlap")
67	}
68	encryptBlockGo(c.enc[:c.l], dst, src)
69}
70
71func (c *aesCipher) Decrypt(dst, src []byte) {
72	if len(src) < BlockSize {
73		panic("crypto/aes: input not full block")
74	}
75	if len(dst) < BlockSize {
76		panic("crypto/aes: output not full block")
77	}
78	if alias.InexactOverlap(dst[:BlockSize], src[:BlockSize]) {
79		panic("crypto/aes: invalid buffer overlap")
80	}
81	decryptBlockGo(c.dec[:c.l], dst, src)
82}
83